Cupola slag cement mixture and methods of making and using the same

ABSTRACT

A slag cement mixture and process of making the same is disclosed. The slag cement mixture is composed of cupola slag and portland cement. The cupola slag is optionally ground granulated. One embodiment of the process includes rapidly quenching the slag by submersion into water or by spraying water onto it, and grinding the resulting product to achieve a fineness of at least 6,000 cm 2 /g. The process also includes the addition of 35% ground granulated cupola slag to portland cement to achieve a stronger and harder cement than portland cement alone.

RELATION TO PRIOR APPLICATION

[0001] This application claims priority to U.S. Provisional PatentApplication Ser. No. 60/183,370, filed Feb. 18, 2000.

FIELD OF INVENTION

[0002] The present invention relates to cement. More particularly, thepresent invention relates to a slag cement mixture and a process ofmaking the same. While the invention is subject to a wide range ofapplications, it is especially suited for use in structural concrete andconcrete construction.

BACKGROUND

[0003] Cement is a widely used building material. A particularly popularvariety of cement is portland cement. Portland cement is used in manyapplications such as mortar, concrete, and cement building materialssuch as building blocks. Portland cement is produced by pulverizingclinker to a specific surface area of about 3,000 to 5,000 cm²/g orfiner. Clinker is created in a cement kiln at elevated temperatures fromingredients such as limestone, shale, sand, clay, and fly ash. Thecement kiln dehydrates and calcines the raw materials, and produces aclinker composition comprised of tricalcium silicate (3CaO-SiO₂),dicalcium silicate (2CaO-SiO₂), tricalcium aluminate (3CaO-Al₂O₃), andtetracalcium aluminoferrite (4CaO-Al₂O₃-Fe₂O₃).

[0004] Conventional mortar and concrete compositions contain cement,aggregates such as gravel and sand, and water to activate the hydrationprocess. A mortar product is a hardened cement product obtained bymixing cement, a fine aggregate, and water. A concrete product is ahardened cement product obtained by mixing cement, coarse aggregate,water, and often a fine aggregate as well.

[0005] The strength properties of concrete and mortar products depend inpart on the relative proportions of cement, aggregates, and water. TheAmerican Society for Testing and Materials (“ASTM”) standard testprocedures, such as ASTM C192 and C39 describe the procedures formixing, casting, curing, and testing portland cement concrete mixtureswith 1, 3, 7, 14, and 28 day standards. Greater compressive strength isa desirable feature of cement, and a number of materials have been usedto improve the compressive strength of cements.

[0006] One way of improving the compressive strength of hardened cementis to blend ground granulated blast furnace slag with cement to give animproved cement composition. Blast furnace slag is a by-product of theproduction of iron in a blast furnace consisting of silicates andaluminosilicates of calcium. A quick setting cement can be produced bygrinding blast furnace slag with gypsum. (See, for example, U.S. Pat.Nos. 1,627,237 and 2,947,643). Blast furnace slag has hydraulicproperties very similar to portland cement, and adding blast furnaceslag to cement is routine to increase the cement's strength. (See ASTMSpecification C989).

[0007] Typical North American blast furnace slag composition ranges are3240% SiO₂, 7-17% Al₂O₃, 2942% CaO, 8-19% MgO, 0.7-2.2% SO₃, 0.1-1.5%Fe₂O₃, and 0.2-1.0% MnO. (see The Portland Cement Association Researchand Development Bulletin RD112T). Blast furnaces in the U.S. areoperated using a basic slag, typically defined as the slag ratio: (%CaO+% MgO)/(% SiO₂+% Al₂O₃), where the slag ratio is maintained inexcess of 1.0 in order to remove sulfur from the iron produced and tofacilitate producing an iron of high carbon content. The chemicalcomposition of blast furnace slag also varies world wide, especially inalumina content. Blast furnace slags have long been recognized as veryuseful commodities and have been used in a number of applications. Inaddition to its use as cement additive, blast furnace slag has been usedin asphalt, sewage trickle-filter media, roadway fills, and railroadballast.

[0008] Blast furnace slags can be used to prevent excessive expansion ofconcrete mixtures that have a high-alkali content and aggregates thatare alkali-reactive. Use of blast furnace slag as 40% or more of such acement mixture can prevent excessive expansion. Blast furnace slag ischaracterized by its short setting time, which is the time between theaddition of mixing water to a cementitious mixture and when the mixturereaches a specified degree of rigidity as measured by a specifiedprocedure.

[0009] Steel slag is also used as a cement additive. Steel slag isformed in the process of making steel in a blast furnace, and often hasa high concentration of ferrites. Because of its high ferritecomposition, steel slag is generally used as a filler in cement roadbuilding material or as a feedstock raw material in cement kilns. It ispossible to produce a hydraulic cement base from steel slag by addingfurther minerals to the slag portion, thereby reducing the ferritecomposition of the slag. This additional step, while rendering a usableproduct, is costly and time consuming.

[0010] Mixtures of blast furnace slag and steel slag have resulted instronger cement products, but cupola furnace slag, a by-product of castiron production, is only rarely used in cement except as a processingaddition. (See ASTM C465 and Cupola Handbook, published by the AmericanFoundrymen's Society). Blast furnaces and cupola furnaces are operateddifferently and are used to make different iron products, consequently,the slag products of these furnaces are also different, both in chemicalcomposition and in material properties. Cupola slag has differenthydraulic properties than blast furnace slag. For example, cupola slagblended cement sets more slowly and at 7 days lacks the strength ofblast furnace slag blended cements. Also, cupola slag is not a commonconcrete additive due to environmental concerns such as the possibilityof rain water leaching out some of its components. Indeed, cupola slagoften presents a disposal problem, which creates an additional expense,ultimately increasing the cost of the iron produced.

[0011] There is an ever present need in the cement art for harder,stronger cement products with longer setting times. There is also a needin the cast-iron production art for a disposal method for cupola slagthat is environmentally safe and economically practical.

SUMMARY OF THE INVENTION

[0012] Accordingly, the present invention is directed to a cupola slagblended cement with an increased compressive strength. The principaladvantage of the present invention is a cement mixture that results in aconcrete which is both harder and stronger while providing a means ofrecycling cupola slag that is both environmentally sound andeconomically practical. The cement compositions of the present inventionhave a resistance to expansion due to sulfate attack and alkali silicareaction, and can be formulated to have a wide range of curing times.

[0013] To achieve these and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described, theinvention is a hydraulic cement containing cupola slag ground to afineness of greater than 4,000 cm²/g blended with portland cement. Apreferred embodiment of the invention is a hydraulic cement containingcupola slag ground to a fineness of greater than 5,000 cm²/g blendedwith portland cement. In the most preferred embodiment, the invention isa hydraulic cement containing cupola slag ground to a fineness ofbetween 6,000 cm²/g and 7,000 cm²/g.

[0014] In one embodiment, the invention is a hydraulic cement containingfrom about 20 to 50% of a ground granulated cupola furnace slag blendedwith portland cement. In a preferred embodiment, the invention is ahydraulic cement containing from about 30% to 40% cupola slag blendedwith portland cement. In another preferred embodiment, the invention isa hydraulic cement containing about 35% cupola slag blended withportland cement.

[0015] The invention includes ground granulated cupola furnace slag witha fineness of about 5,000 to about 7,000 cm²/g and meeting the finenessrequirement of the ASTM C989 Grade 100 specification for blast furnaceslag.

[0016] The invention includes ground granulated cupola furnace slag witha fineness of about 6,000 to about 6,750 cm²/g. The invention alsoincludes ground granulated cupola furnace slag with a fineness of about6,500 cm²/g.

[0017] In one embodiment of the invention, a blended cement mixture ofabout 35% cupola furnace slag displays a 28 day compressive strength ofmore than 7,000 psi and a flexural strength of more than 700 psi.

[0018] In another embodiment of the invention, the total heat ofhydration of the blended cement mixture of about 35% cupola furnace slagdoes not exceed 250 J/g when measured for 72 hours, and the expansion ofmortar bars does not exceed 0.20% at when measured at 14 days.

[0019] In one embodiment, the invention includes a process of usingcupola slag as a raw cement kiln feedstock.

BRIEF DESCRIPTIONS OF THE DRAWINGS

[0020]FIG. 1 shows the results of conduction calorimetry tests performedon two neat cement pastes: standard portland cement (darker line), and aportland cement/cupola slag blend (lighter line).

[0021]FIG. 2 shows the results of compressive strength tests performedon concrete objects made with the same aggregates, but using eitherstandard portland cement (solid line), or a 65/35% blend of portlandcement and cupola slag (dashed line).

[0022]FIG. 3 shows the results of X-ray powder diffraction testsperformed on cupola furnace slag (upper diffractogram) and on blastfurnace slag (lower diffractogram).

DETAILED DESCRIPTION OF THE INVENTION

[0023] The present invention encompasses blends of cupola slag andcement with an increased hardness and strength than the cement alone.

[0024] The hydraulic cement compositions of the present inventionprovide a solution to the current needs of the art by converting cupolafurnace slag into a useful product. The cement compositions of theinvention can be formulated to have a wide range of resistance tosulfate attack as well as wide range of curing times so that they can beused for a variety of purposes such as making concrete objects. Inparticular, a hydraulic cement containing 35% of a ground granulatedcupola furnace slag, with a fineness of at least 6,000 cm²/g and meetingthe fineness requirement of the ASTM C989 Grade 100 specification forblast furnace slag blended with portland cement creates a compositionwhose superior compressive strength develops slower than the concretescurrently in use thus providing a more durable concrete product.Additionally, the sulfate attack resistance of the present inventionincreases the useful life of any products made from cupola furnace slagblended cements thereby increasing the length of time between replacingsuch products and reducing the overall cost of any such project.

[0025] The chemical composition of portland cement plays an importantrole in the way that slag blended cements cure, age and resist chemicalattack. The processing of portland cement is well known in the art, asare the various methods to alter the chemical composition during themanufacturing process. The invention is not, however, limited toportland cement. It is believed that cupola slag mixed with othercements will improve the strength of the cement/cupola slag mixture.

[0026] A cupola furnace is a vertical shaft furnace used to produce castiron by high temperature melting of metallic and mineral chargematerials. A cupola furnace contains a continuous melting shaft whichcan accept a wide range of raw materials including oily, wet andcontaminated scrap. Compared to batch-type furnaces, the energyrequirements of a cupola furnace are low. Molten iron is tapped from thebottom of the furnace. Slag is removed in a molten state via a slaghole. Cupola furnace slag is preferably rapidly quenched by submersioninto water to yield a fine, granulated product, thus reducing the amountof grinding required to make the slag useful in cement. Alternatively,water may be sprayed upon the slag to quench it, or the slag may beallowed to air-cool for a time, resulting in a coarser, non-granulatedproduct.

[0027] Cupola furnace slag differs from blast furnace slag in chemicalcomposition; for example, cupola slag has a higher silica content and alower calcium oxide content than blast furnace slag. While blastfurnaces operate using a basic slag, cupola furnaces generally operateusing an acid slag for the production of gray cast iron. (Basic slagsare sometimes used in cupola furnaces for the production of ductile ironbecause the basic slag removes sulfur in the cupola during melting).Blast furnace operations produce about 30 percent slag per ton of molteniron, while cupola furnace operations produce 5 to 6 percent slag perton of iron ore that is melted.

[0028] Cement users are particularly interested in setting and strengthdevelopment characteristics. The maximum and minimum setting times andminimum strengths of reference cement are specified in the ASTM C150standard specification for portland cements. A number of minorcomponents which form in the clinker from impurities present in the rawmaterials or fuel can influence both the clinker formation process andthe hydraulic reactivity and cementitious properties of the resultingcementitious material. In particular, the level of alkalis, such as K₂Oand Na₂O present in cement, especially portland cement, may be ofconcern. For example, if the cementitious materials are combined withaggregates containing SiO₂, the alkalis present in the cementitiousmaterials may react with the SiO₂ to form an expansive alkali silicagel, which can lead to cracking and break up of the concrete structure.Because the detection of reactive SiO₂ in aggregates is difficult,cementitious materials with low alkali content are generally used. Blastfurnace slags are generally very basic in nature. Thus, a maximumequivalent Na₂O of about 0.6 percent is included as an optional limit inthe ASTM C150 specification.

[0029] It is possible to use cement containing more than 0.60 percentequivalent Na₂O with SiO₂ reactive aggregates while avoiding excessiveexpansion and reducing the total energy used to manufacture the cement.One example is to mix cement, preferably portland cement, with latentlyhydraulic materials such as ground granulated blast furnace slag.However, the latently hydraulic materials do not react as quickly asportland cement, and as a result they contribute to the later developedcement strength rather than the earlier. The decreased early activityresults in lower heats of hydration, which leads to thermal crackformation. However, the addition of blast furnace slag does noteliminate thermal crack formation.

[0030] ASTM C125-99a “Standard Terminology Relating to Concrete andConcrete Aggregates” defines a number of terms that apply to hydrauliccement. It is well known in the prior art, that the hydraulic propertiesof blast furnace slag vary greatly upon the chemical nature of the blastfurnace slag and the way that molten slag is cooled.

[0031] Blast furnace slag is classified by performance in the blastfurnace slag activity test in three grades, Grade 80, Grade 100, andGrade 120. ASTM specification C989 outlines the strength development ofportland cement mixed with the three strength grades of finely ground,granulated blast furnace slag as measured at seven days and twenty-eightdays and expresses this as blast furnace slag activity index (SAI). Whenblast furnace slag is used in concrete with portland cement, the levelsand rate of strength development depend on the properties of the blastfurnace slag, the portland cement, the relative and total amounts of theblast furnace slag and the cement as well as the cement curingtemperatures. Unless the slag is derived from a blast furnace it cannotbe marketed as blast furnace slag under the ASTM C989 standards.

[0032] ASTM C989 specifies that the reference cement used to test blastfurnace slag activity have a minimum 28-day strength of 35 MPa (5,000psi) and an alkali content between 0.6 and 0.9%. To properly classify ablast furnace slag, the reference portland cement must conform to thelimits on strength and alkali content under ASTM specification C989.Test data indicate that concrete compressive strengths at 1, 3 and even7 days tend to be lower using blast furnace slag cement combinations.Generally a higher numerical grade of blast furnace slag can be used inlarger amounts and will provide improved early strength performance, buttests must be made using job materials under job conditions to properlyaccess the performance of a blast furnace slag cement.

[0033] Blast furnace slag has latent hydraulic properties that requirean activator to realize these hydraulic properties. One way for slag toacquire hydraulic properties is to rapidly quench the slag to preservethe molten slag in a vitreous state. Two processes that are commonlyused to activate the slag's hydraulic properties are granulation andpelletization. In the granulation process, slag is quenched by theinjection of a large quantity of water under pressure into the slag. Ifthe temperature of the slag is above its melting point prior toquenching, then quenching produces a wet sand-like material with a highdegree of vitrification. But if the slag is permitted to cool slowly, itcrystallizes and exhibits reduced hydraulic properties. To achieve thedesired fineness, the granulated slag is dried and ground. Blast furnaceslags are typically ground to a specific surface area of 5,000 to 6,500cm²/g. A fineness of greater than 6,500 cm²/g requires additional stepsand is more difficult to achieve on a large industrial scale under dryconditions. Another measure of specific surface area is the Blaine airpermeability method. The Blaine Fineness test is described in ASTM C204“Standard Test Method of Hydraulic Cement by Air PermeabilityApparatus.” There, blast furnace slags are described as having aspecific surface area of 5,000 to 6,500 cm/²g. The early development ofhigh strength is a characteristic of cements comprising blast furnaceslag ground to a fineness of 7,500 cm²/g. As the fineness increases sodoes the rate of the hardening reaction. As ground granulated blastfurnace slag typically has a fineness of about 5,000-6,500 cm²/g, anextra grinding step is required to achieve a fineness of 7,500 cm²/g.There is an energy cost for the extra grinding step, but itsubstantially improves the mechanical strength of the resulting cement.Greater specific surface areas generally result in greater initialstrengths.

[0034] Cupola furnace slag can be granulated by the process of slagquenching. Molten cupola furnace slag is granulated by the injectioninto the slag of a large quantity of water under pressure, producing awet sand like material with a high degree of vitrification. The degreeof vitrification depends on the slag temperature prior to injection andthe temperature of the water under pressure. Because cupola slag has alower sulfate and magnesium content and a higher silica and iron oxidecontent there is a decrease in the heat generated, which is advantageousfor increasing setting time and slowing the initial strength gain of theconcrete. The lower sulfate and magnesia content coupled with a highersilica and iron oxide content also leads to a reduction in theexpansions due to heat of hydration and alkali silica reaction.

[0035] For the purpose of illustrating the advantages obtained by thepractice of the present invention, plain concrete mixes were preparedand compared to similar mixes containing cupola slag. The followingexample is illustrative and is not intended to be limiting. The methodsand details were in accordance with current applicable ASTM standards.

EXAMPLE 1

[0036] Cupola furnace slag useful in cement compositions of the presentinvention desirably shows the following components upon analysis: TABLE1 Composition of Cupola Slag Component Proportion (wt. %) SiO₂ 43.87Al₂O₃ 8.5 Fe₂O₃ 1.93 CaO 33.3 MgO 3.38 SO₃ 0.30 Na₂O 0.10 K₂O 0.30 TiO₂0.34 P₂O₅ <0.01 Mn₂O₃ 1.18 SrO 0.08 L.O.I. (950° C.) 4.34 Total 97.84Alkalies as Na₂O 0.30

[0037] Although only applicable to blast furnace slag, the Slag ActivityIndex test as described in ASTM C989 “Standard Specification for GroundGranulated Blast Furnace Slag for Use in Concrete” was performed on thecupola furnace slag as well as a Blaine Fineness test as described inASTM C204 “Standard Test Method of Hydraulic Cement by Air PermeabilityApparatus.” Table 2 shows the results of these two tests for twodifferent cupola slag samples ground using a 40-lb mill to two differentfineness values similar to those of commercially available blast furnaceslags. TABLE 2 Fineness and Slag Activity Index data Ground Cupola ASTMC989 Slag Sample Requirement for: No. 1 No. 2 Grade 80 min Grade 100 minFineness, cm²/g 4240 6530 — — Slag Activity At 7 days 61 73 — 70 Index,% of At 28 days 98 124 70 90 control

[0038] As evident from Table 2, both samples exceeded the ASTM C989 SAIrequirements for Grade 80 and Grade 100 blast furnace slag at 28 days.Sample 2 met the SAI 7 day requirements for Grade 100 as well. Based onthis test, all additional tests were preformed on Sample 2

[0039] Conduction calorimetry tests were conducted on neat cement pastesmade with the control cement and with cupola furnace slag blend byinjection-mixing of 2 grams of cement with water inside a calorimetercell. The slag used in this test was Sample 2 as it met the ASTM C989Blast Furnace Slag Activity Index requirement for 7-day and 28-day ofcommercially available blast furnace slag Grade 100. The heat ofhydration was recorded over a 72 hour period. The first peak representsthe heat reaction as the cement comes into contact with the mix water.After the initial peak there is a period of relative inactivity duringwhich the paste remains plastic. The second peak indicates anaccelerated reaction during which the alite in the cement hydratesrapidly and heat is generated. The initial setting of the paste occurssoon after the beginning of the acceleration period and the finalsetting occurs towards the end of the acceleration period. A maximum inheat evolution is reached soon after the final set, after which the heatevolution declines to a steady state. The heat of hydration is afunction of both the chemical and the physical properties of the cement.Table 3 shows the results of the calorimetry tests. TABLE 3 HeatGeneration Data for Portland Cement and Cupola Furnace Slag BlendedCement Control Cupola Slag Blend Rate of heat Rate of heat generationTotal Heat generation Total Heat Description Time J/Kg/sec J/g TimeJ/Kg/sec J/g Initial 2.28 min 48.74 3.35 3.48 23.55 2.51 Hydration PeakTotal Heat at: 0.5 hr 15.43 0.5 hr 11.07 Onset of Alite 2.15 hr 0.5920.15 3.09 hr 0.51 17.26 Hydration Peak of Alite 11.20 hr 2.91 71.1715.30 hr 2.70 89.28 Hydration Total Heat at: 24 hr 169.61 24 hr 140.91Total Heat at: 48 hr 235.70 48 hr 193.40 Total Heat at: 72 hr 264.33 72hr 223.19

[0040] Table 3 indicates that the initial hydration peak for cupola slagcement occurs later in time than that of the control cement andgenerates heat at a much slower rate and generates a lot less heat.Total heat one half hour after hydration is considerably lower forcupola furnace slag as well. Another major difference between thecontrol cement and the cupola furnace slag cement is that the onset ofalite hydration and the peak of hydration are both much later in thecupola slag cement than in the control. Initially the total heatreleased for alite hydration is lower for the cupola slag cement but bythe time the peak of alite hydration occurs, the total heat generated ishigher for the cupola slag cement than the control cement. Total heatreleased overall remains lower for the cupola slag cement at each of thetime periods measured. It is anticipated that the surprising low-heatproperties of the cupola slag cement will make it particularly useful inmaking concrete that is adapted for mass concrete pours such as raftfoundations, bridge decks, piers, and dams.

[0041] Resistance to sulfate attack on Sample 2 was tested in accordancewith ASTM C1012 “Standard Test Method for Length Change ofHydraulic-Cement Mortars Exposed to a Sulfate Solution”. The expansionof the control and the blended cupola furnace slag cement at 15 weekswas 0.026 and 0.015% respectively.

[0042] The potential for the cupola slag to modify alkali reactivity wasdetermined using ASTM C1260 “Standard Test Method for Potential AlkaliReactivity of Aggregates (Mortar Bar Method)”. The cement used in thistest was the cupola furnace slag bend of sample 2, and the aggregate wasa highly reactive graded Albuquerque sand. Table 4 shows the results.TABLE 4 Expansion of Bars Due to Alkali Silica Reaction Expansion, %Age, Days Control Cupola Slag Blend 0 0.000 0.000 5 0.009 0.013 11 0.3490.77 14 0.580 0.195

[0043] Table 4 indicates that the potential of cupola slag to modifyalkali reactivity is considerably lower for cupola slag at days 11 and14 than the control.

[0044] Compression and flexural strengths of a blended cement containing35% cupola furnace slag (Sample 2) was measured at day 3, day 7, day 28,day 56 and day 90 and compared to a control cement measured with thesame age in days. No chemical additives were added to either mix and themixes were made with the same cementitious content as well as the samewater to cementitious ratio. The mix portions of the two cements areshown in Table 5 while the results of the compression and flexural testsare shown in Table 6. TABLE 5 Concrete Mix Proportions Mix ProportionsMaterial Control Cupola Slag Blend Portland Cement, pcy* 654 426 Slag,pcy 0 229 Eau Claire sand, pcy 1,342 1,336 Eau Claire ¾″ stone, pcy1,847 1,849 Water, pcy 266 267 Slump, inches 5 7

[0045] TABLE 6 Compressive and Flexural Strength Results CompressiveStrength Flexural Strength (ASTM C39), psi (ASTM C78), psi Cupola SlagCupola Slag Age, Days Control Blend Control Blend 3 4,410 2,570 — — 75,530 4,320 785 490 28 7,150 7,780 750 755 56 7,530 8,740 770 750 907,710 8,630 — —

[0046] Table 6 demonstrates that the cupola slag blended cement at days3 and 7 displays a lower compressive strength when measured using theASTM C29 method. By day 28, however, the compressive strength of thecupola slag has surpassed that of the control cement, a totallyunexpected result. Additionally, the compressive strength of the cupolaslag blended cement unexpectedly continued to increase until after day56 where it begins to level off. At day 56 the compressive strength ofthe cupola slag blended cement is more that 1,200 psi greater than thecontrol cement. These tests indicate the surprising result that thecupola slag blended cement makes superior concrete over that made withconventional cements. Table 6 demonstrates that the flexural strength ofthe cupola slag blended cement as measured by the ASTM C78 methoddevelops at a slower rate than that of the control but after 28 days isapproximately equal to that of the control cement.

[0047] X-Ray Diffraction Analysis

[0048] X-ray diffraction may be used to identify and quantifycrystalline materials. Crystalline materials consist of orderedarrangements of atoms in three-dimensional arrays. Such arrays havecharacteristic spacings between the layers of closely packed atoms. Thelength of the spacings vary by atom size and the three dimensionalarrays.

[0049] When a powdered sample is subjected to a beam of radiation froman X-ray source a diffraction pattern is created. The X-ray beampenetrates the powder a short distance and diffracts from the mostdensely packed layers of the atoms within the powdered sample. The X-raybeam is rotated through a series of angles relative to the surface ofthe powdered sample. When the signal from the diffracted beam isparticularly strong, the distances between layers of atoms (thed-spacings) can be calculated as multiples of the wavelengths of theincident radiation and the incident angle.

[0050] A crystalline material has a characteristic pattern of relativepeak heights at given angles. Mixtures of crystalline materials displaycombinations of these patterns and the relative peak heights fromvarious materials can be used to quantify the relative concentration ofeach crystalline material. X-ray diffraction may also be used toidentify cracks in concrete. The detection limit for X-ray will dependon the type of material analyzed and it can be as high as 5 to 10%.

[0051] A ground granulated cupola furnace slag sample was finelypowdered and subjected to XRD analysis on a Philips PW 1720 X-raydiffractometer (CuKθ) equipped with a θ-compensating slit, graphitemonochromator, gas proportional counter detector, pulse height selectorand a strip chart recorder. A commercial granulated blast furnace slagsample was also finely powdered and analyzed as a control. Each samplewas scanned from 65°2θ to 6°2θ at a rate of 1°2θ per minute. Table 7 isa summary of the phases detected by XRD. TABLE 7 X-ray DiffractionAnalysis Sample Largest Phase Detected Crystalline material CupolaFurnace Slag Amorphous material with a SiO₂ (α-quartz) peak at 29.8° 2θBlast Furnace Slag Amorphous material with a CaCO₃ (calcite) peak at 31°2θ

[0052] As can be seen from Table 7, the two slag samples vary in theircrystalline composition as well as their non-crystalline or glassycomposition. The cupola slag sample has an amorphous phase peak at29.8°2θ (lower angle) indicating a larger d-spacing than that of theblast furnace slag. The XRD analysis also shows that crystalline SiO₂ ispresent in the cupola slag which suggests a more acidic form of theamorphous phase. The amorphous phase of the cupola slag probablycontains of higher amounts of not only SiO₂ but also Al₂O₃ and Fe₃O₃than the blast furnace slag.

[0053] All references and standards cited herein are incorporated intheir entireties.

1. A cement mixture comprising cupola slag blended with a. conventionalcement, wherein the cupola slag is ground to a fineness greater than4,000 cm²/g. 2-28. (Canceled).